Treatment of tobacco smoke to reduce metal carbonyl content thereof



Oct. 21, 1969 E. E. STAHLY 3,47

TREATMENT OF TOBACCO SMOKE TO REDUCE METAL CARBONYL CONTENT THEREOFFiled Oct. '2, 1968 BRAND A POROUS PAPER FOR. AVERAGE I5! AIR DILUTION(CIGARETTE BRAND A) TO TOBACCO TREATED WITH UREA PEROXIDE HOLES D &ASIZED TO GIVE AIR. DILUTION OF 0.4 VOLS PER VOL SMOKE HOLES SEALED WITHA FUSIBLE MATERJAL- HOLE OPEN UP ABOUTJ. CM BEHIND THE BURNING ZONE FIG.4

F I 1 J A B C POROUS PAPER. covsams B AND c ADMITS INITIAL AIR FOR. 0.25DILUTION FIG. 5

IN VE N TOR ELUON E. STAHLY Zw w A TTORNEV United States Patent US. Cl.131-9 1 Claim ABSTRACT OF THE DISCLOSURE Highly toxic metallic carbonylsare removed from tobacco smoke by oxidation by extraneously introducedoxygen derived in part from heat decomposable peroxy compounds withwhich the tobacco is impregnated and in part from air introduced throughpores or perforations in the tobacco wrapper of a smoking device such ascig arettes, pipes, cigars, or the like.

The present invention is a continuation-in-part of my copendingapplication, Ser. No. 303,929, filed Aug. 22, 1963, now abandoned,entitled Cigarette Air Dilution for Oxidation of Carbonyls.

This invention relates to a method of improving tobacco smoke byreducing the metal carbonyl content of the smoke. More particularly,this invention relates to controlled introduction of oxygen into tobaccosmoke in smoking devices, e.g., cigarettes, cigars, and pipes, theoxygen being derived both from air and other chemical sources, theoxygen serving to oxidize and destroy metal carbonyls, to produce smokewhich is free of metal carbonyls.

The term metal carbonyls as used herein refers to compounds of a metaland carbon monoxide and, in addition, to compounds containing only ametal and CO, including metal nitrosyl carbonyls and metalhydrocarbonyls, wherein the metal-carbonyl combination also containsnitrosyl (NO) and/ or hydrocarbonyl (COH) groups respectively.

Objects of the invention severally and interdependently are to providean improved tobacco smoke free of metal carbonyls; provide an improvedcigarette smoke free of metal carbonyl as compared to conventionalcigarettes; improved cigar and pipe smoke as compared to conventionalcigar and pipe smoke; an improved method for conventional smokingdevices which will provide an improved tobacco smoke from which thenickel carbonyls are substantially eliminated to meet standards set bygovernment hygienists for maximum atmospheric concentrations of nickelcarbonyl; and an improved tobacco smoke from which the metal carbonylsare substantially eliminated by introduction of both air and a materialwhich releases oxygen to dilute the tobacco smoke.

in combustion of tobacco in conventional smoking devices, some carbonmonoxide is formed. The carbon monoxide contents of tobacco smoke havebeen found to vary from 4 to 11 volume percent, in spite of an ap parentsufiiciency of air for complete oxidation of CO to C0 The amount of COpresent is presumably dependent in part on the ratio of oxygen totobacco in the combustion zone. The carbon monoxide will not be oxidizedfurther outside the combustion zone in the absence of a catalyst, andhence is always present in significant amounts in the smoke in theunburned portions of the cigarette.

3,473,535 Patented Oct. 21, 1969 ice Metal carbonyl formation appears tobe dependent on the reaction of the carbon monoxide with metal compoundsor complexes present in the tobacco in the cooler, unburned portions ofthe tobacco because, as is known, iron, cobalt, and nickel carbonylscompletely dissociate at C. to 200 C., and could not form in the muchhoter, burning ember. Thus these volatile metal carbonyls form behind orbelow the combustion zone of a cigarette, cigar or pipe. To demonstratesuch formation of metal carbonyls, a gas containing 7 percent carbonmonoxide was passed over cigarette tobacco at atemperature of 50 C. andit was found that the nickel content of the tobacco was reduced from 10micrograms per gram to 1 microgram per gram; cobalt content from 1.3micrograms to 0.1 microgram per gram; and iron from 330 to microgramsper gram of tobacco.

Conventional tobacco smoke, more particularly, conventional cigarette,cigar and pipe tobacco smoke, contains substantial traces of metalcarbonyls, especially of nickel, cobalt and iron carbonyls which areremoved from the smoke by the present invention.

The present invention removes metal carbonyls from tobacco smoke byintroducing air lateraly through the side walls of the smoking devicesuch as the cigarette paper and simultaneously enriching the air withoxygen derived from an oxygen evolving chemical compound such as aperoxy compound which releases oxygen by warming by the smoke.

The invention is further described with relation to the drawing wherein:

FIG. 1 shows graphically the efiect on carbonyls by equivalent airdilution;

FIG. 2 illustrates a cigarette having porous paper in which the tobaccohas been impregnated with urea peroxide as a typical peroxy compound;

FIG. 3 shows a paper having perforations and a filter at the left handend near the uppermost perforations;

FIG. 4 illustrates a cigarette having sealed perforations to impart arelatively constant air dilution during smoking; and

FIG. 5 illustrates a filter cigarette having only a limited portion,such as one-third to two-thirds filled with tobacco treated with aperoxy compound and the balance comprising both empty space and filter.

As shown in the drawings, FIG. 1 illustrates that the carbonyl contentof smoke is reduced rapidly by introducing an oxidizing agent air andoxygen released by a peroxy compound which may approach 0 at about 0.3part of air per part of smoke. As equivalent air dilution, the sameeffect will result if the oxygen is supplied chemically by the peroxycompound or the oxygen in the air, both being preferred herein. That is,oxygen preferably is supplied by a combination of oxygen-releasingperoxy compound and air. It is obvious that at least 0.3 equivalent airdilution parts per part of smoke is needed to completely destroy thecarbonyls in the smoke.

Introduction of air laterally through the walls tends to destroy thesmoking pleasure and the resistance to the drawing through a cigarette.Obviously the dilution by air should be held to a minimum, a practicallimit being about 1 part of air per part of smoke and preferably theintroduced air is not over 0.5 part of air per part of smoke. As theoxygen is also supplied by the tobacco impregnated peroxy compound, thequantity of laterally introduced air as a source of oxygen may beprogressively reduced. The combination of both, however, allows moreaccurate control of the quantity of oxygen released since the use of theperoxy salt alone can release all of the oxygen required to oxidizecarbonyl in the smoke.

FIG. 2 illustrates a cigarette where 0.15 percent of air is drawn inlaterally through a porous cigarette paper, and the tobacco is treatedwith sutficient urea peroxide to release the required remainder. It willbe appreciated that the even distribution of the peroxy compound readilyovercomes the reduction of porosity of the paper, progressively as thecigarette is consumed, and the lateral wall of cigarette paper becomesdiminished thereby. The reduced quantity of air is supplemented at leastto present an adequate quantity of oxygen to oxidize the carbonyls byoxygen released from the peroxy compound.

FIG. 3 shows a filter cigarette having a filter E and two rings ofperforations D near the filter, and A, at an upper intermediate point.The body of the cigarette paper B may or may not be porous. However, thequantity of air introduced through A and D with a selected porosity, asdesired of the paper in the area C, is sufficient in combination withthe peroxy compound with which the tobacco is impregnated to adequatelyoxidize the carbonyls in the smoke as the cigarette is being consumed.

FIG. 4 illustrates another modification of a perforated cigarette paperabout a cigarette having a filter. The perforations in this case aresealed with a low melting wax such as paraflfin, tallow or stearin,whereby the perforations in the paper become progressively opened bymelting of the wax therein, just behind the hot ember of the cigaretteas the cigarette is being consumed.

FIG. 5 illustrates a cigarette in which a lower portion C of thecigarette contains tobacco, and an empty space B is, as well as theportion C, covered overall by porous paper. A cigarette filter A can bemounted on the end of B. At the beginning of smoking of the cigarette,air is introduced through the porous paper of both B and C sections. Thetobacco present only in the C section is also impregnated with a peroxycompound. According to such modification the carbonyl content of thesmoke is destroyed both in the tobacco section C and in the emptysection B. This oxidation of carbonyls in the smoke is accomplished byintroduction of at least the minimum volume of air and oxygen which Ihave found necessary to reduce the metal carbonyl contents. For example,the smoke behind the combustion zone, in either non-filter or filtercigarettes, cigars, or pipes, while it contains some unused air,requires a certain minimum additional oxygen supply thereto to eliminatethe metal carbonyls from the smoke.

The procedure employed in demonstrating the present invention was: (1)the smoking of a group of sixty cigarettes, each of three brands (D, Band A) to serve as controls. The method of scrubbing of the smoke andanalysis for nickel carbonyl was used by F. W. Sunderman, Sr., and F. W.Sunderman, Jr. (American Journal of Clinical Pathology, 35, pp. 203-209,1961) wherein alcoholic iodine solution and nitric acid scrubbers absorbed carbonyls of iron, nickel and cobalt from the smoke; (2) sixtycigarettes were smoked for each example.

These values for metal carbonyl contents of the smoke were confirmed byanalysis of tobacco of the unsmoked cigarette, together with the butttobacco and ashes of the smoked cigarette; when filter cigarettes weretested the filter was analyzed before and after smoking to obtaincontents of iron, nickel and cobalt. These analytical determinations onthe tobacco, ashes and filters were made by a combination of chemicaland spectrophotometric methods.

The smoking was accomplished by a mechanical smoking system wherein 35ml. pufis were taken in, collecting about 350 ml. of smoke for controltests, and 500 ml. or more in the dilution tests utilizing my invention.The 35 ml. were made in a measured manner by use of a bulb which, onexpansion, drew 35 ml. of smoke, and on compression passed the puff ofsmoke into the scrubbing system described by Doctors Sunderman (as citedabove Further details are given as required in the descriptions of theindividual examples. Examples I through VI show the dilution which Ihave found necessary with the three brands of cigarettes identifiedabove.

EXAMPLES IVI.AIR DILUIION vs. METAL IN TOBACCO SMOKE CARBONYLSMicrograms or metal carbonyls While variations in metal contents oftobacco may require provision of different minimum amounts of airdilution to eliminate the metal carbonyls from the tobacco smoke, myinvention is 'based on a controlled dilution of the tobacco smoke withadditional oxygen, so that all metal carbonyl contents are eliminated.The diluent with oxygen is effected by introduction of air into thesmoking device and introduction of oxygen in a combination of air andoxygen.

Air and oxygen in controlled amounts are introduced into tobacco smokebehind the combustion zone of the tobacco. The air and oxygen areintroduced in an amount sufficient to decompose the metal carbonylsalready formed; or, if introduced immediately behind the combustionzone, the formation of the metal carbonyls can be prevented by theexcess of air.

Such controlled introduction of air and oxygen in cigarettes is effectedin the present invention in two ways:

(a) By providing openings in the cigarette paper, of controlled surfacearea from 10 to 20 mm. in front or the present conventional filter; or,for non-filter cigarettes, from 10 to 20 mm. from the mouth end of thecigarette, the month end being the end which enters the smokers mouth,thus introducing a constant amount of air with each pufi; and

(b) By incorporating a compound into the tobacco formulation whichreleases oxygen into the smoke as it is warmed to 60 C. to 200 C.

Each provision, (a) and (b) reduces the metal carbonyls in the smoke bya mechanism as discussed above.

The use of a uniformly porous paper alone is not successful formaintaining the required low metal carbonyl content of the smoke,because if the porosity is properly adjusted for the full unsmokedcigarette there is not sufiicient air introduced in the partly smokedcigarette to maintain sufficiently low metal carbonyl content in thecigarette smoke.

Of course, excess air can be introduced by use of a high porosity paper,but smoking pleasure is correspondingly reduced as the air dilutionexceeds 1 volume air per volume of smoke. By the data contained inExamples IVI, at least 0.3 volumes of oxygen enriched air per 1.0 volumeof smoke are provided. For pleasure not more than 1.0 volume of air per1.0 volume of smoke is provided by my invention. The oxygen enrichment,0.06 to 0.2 volumes of oxygen per 1.0 volumes of smoke, is provided viaoxygen releasing additives.

The oxygen-releasing additives to be used in this invention must notdeleteriously affect the tobacco or the tobacco smoke and, for thispurpose, are preferably peroxy compounds. Examples of useful peroxyadditives are shown in the table below.

TABLE 1.OXYGEN RELEASING ADDITIVES OF THIS INVENTION Grams to WeightTemp. produce percent Melt. 01 C.) 30 m1. available pt., for O Addit veoxygen oxygen C. release Sodium perborate:

Monohydrate 0. 27 100 100 Trihydrate 0. 4 10 63 63 Lithium perborate 0.2 100 Sodium phosphate peroxyhydr 0.45 9 100 Ammonium perborate 0. 2 20100 Potassium superoxide 0. 12 34 380 l 100 Urea peroxide 0.24 17 80 80Sodium carbonate peroxyhrydata. 0. 29 14 KQCZOG 0.25 16 200 200 NtlgCO40.31 13 Tertiary butyl hydroperoxide 0.25 16 200 Releases oxygen uponcontact with C0, 00 or H 0. 2 Liquid.

These agents or additives may be incorporated into the tobacco by one ofthe following methods: (1) impregnating from an aqueous solution anddrying at temperatures below 50 C.; (2) addition in solution in thehumectant which can be glycerin, propylene glycol, etc.; (3) painted onthe inside of cigarette paper in aqueous or propylene glycol or glycerinsolution; (4) mechani cally mixing the powdered additive with thetobacco in the amount calculated for practice of my invention.

Potassium super oxide is most advantageously mixed with the tobacco foruse in pipes, cigars or cigarettes by a mechanical blender, either batchor continuous. Since it reacts with moisture, the K0 particles mustfirst be coated with a polymer from a non-aqueous solvent, e.g.cellulose triacetate solution in chloroform, so that moisture of thetobacco does not react with it during storage. It is less convenient toemploy potassium superoxide than the other additives, but it has theadvantage of release of large amounts of oxygen per unit weight. It isthe only one of the above-listed additives which can oxidize the CO andconvert it to CO at temperatures below 100 C. By the present invention,the contents of the metal carbonyls in tobacco smoke are reduced andsubstantially eliminated, thereby helping to safeguard smokers againstexposure to these volatile and toxic metal carbonyls. The followingexamples further demonstrate the reduction in metal carbonyls effectedby my invention.

EXAMPLE VII Non-filter cigarette brand D made with non-porous cigarettepaper was selected to serve as control. Three cigarettes from each of 10packs of the same carton were dismantled and the tobacco therefrom wascombined and analyzed for iron, nickel and cobalt, and was found to be330, 9.6 and 1.2 micrograms per cigarette respectively. Six cigarettesfrom each of 10 packages from the same carton were smoked, leaving about16% of the tibacco as unsmoked butt tobacco. The butt tobacco from thesesixty cigarettes was analyzed and found to have been reduced in ironcontent, 25% in nickel content and 50% in cobalt content during smoking.Thus, the metal carbonyls were forming and entering the smoker.

EXAMPLE VIII Filter cigarette brand A made with a uniformly porous paperwas smoked to leave about 16% butt tobacco as in Example VII. From sixtycigarettes it was found that about 15% air was admitted through thepaper, i.e. 15 based on the smoke volume obtained in Example VII, and ofcourse this 15% constituted an average of an initially higher percentand a final lower percent, since the air admitted through the paperdecreases during smoking as the amount of paper decreases with progressof smok- The amount of air dilution was calculated from the increase innumber of standard putts required to smoke the cigarettes to 16% buttsover that required with nonporous paper.

EXAMPLE IX Filter cigarettes brand B were used in this test. Tiny holeswere punched in the paper 20 mm. in front of the filter so that thesmoke at the point of the perforation was diluted with an equal volumeof air. The cigarettes were smoked down to the point of the perforations(about 16% butt tobacco). Analysis of the butt tobacco showed thatinstead of a reduction, an increase in metal content had occurred. Thus,nickel content of the butts showed an increase from 5.2 p.p.m. to 8.0p.p.m. The amount of air dilution was calculated as in Example VIII fromthe comparative number of standard pufl's to reach 16% butt tobacco. Thenickel carbonyl of the smoke after dilution with air deposited thenickel metal in the butt tobacco.

EXAMPLE X Forty non-filter brand D cigarettes were smoked as follows:Prior to each putt two holes were punched in the paper about 5 mm. backof the burning zone. Thus air was introduced into the smoke so that thesmoke was diluted with 0.9 volume of air, and the air was introducedearlier in the smoke stream than in Example III. Smoking was stoppedafter 60% of the tobacco was combusted. Analysis of the butt tobaccoremaining showed an increase in iron content of 31% and in nickelcontent of 50%. The degree of air dilution was calculated in the mannerdescribed in Examples II and III.

EXAMPLE XI Sixty brand D non-filter cigarettes were smoked, leavingabout 50% of original tobacco unsmoked. Air was introduced into thesmoke as in Example 'IV via 1.0 mm. holes back of the burning zone. Thesmoke was thus diluted with 0.8 volume of air as calculated from therelative number of pufis required to smoke to a 30% butt both with andwithout the 1 mm. holes or perforations. A 40% increase in nickelcontent was found in the butt tobacco, a 20% increase in iron, andincrease in the cobalt content.

From Examples VII to XI it was calculated that air dilution of from 30to 40% or more was essential to maintain a detectibly unchangedconcentration of iron, nickel, and cobalt in the butt tobacco. This isthe point at which no change in metal contents of the unburned tobaccooccurs; hence no metal carbonyls can be carried to the smoker. ExampleXII was then run with 0.4 air dilution of the smoke.

7 EXAMPLE x11 Sixty :brand B filter cigarettes were smoked afterpunching three holes 0.02 inch in diameter 2 cm. in front of the filter.This gives an approximate dilution of the smoke of 0.4 volume of air pervolume of smoke. Analysis of butt tobacco showed the same content ofiron, nickel and cobalt as ta, sample of the initial unsmoked cigarettetobacco from the same carton of cigarettes, i.e., 122 p.p.m. iron, 2.8p.p.m. nickel and 0.5 p.p.m. cobalt. (Each cigarette contained about 1gram of tobacco.)

A control test with sixty cigarettes of the same brand B cigarettes fromthe same carton, but without air dilution gave a butt tobacco containing100 p.p.m. iron, 2 p.p.m. nickel, and 0.3 p.p.m. cobalt. This controltest confirms that iron, nickel and cobalt carbonyls are formed (fromthe unsmoked tobacco) when air dilution is not employed in accordancewith my invention.

EXAMPLE XIII Example XII was repeated, using twice as many perforationsto effect air dilution of the smoke so that two volumes of air wereintroduced behind the combustion zone. This effected the same results indepositing metals on the final butt tobacco via initial formation of thecarbonyls behind the combustion zone. However, the taste of the smokewas noticeably altered. Thus, large amounts of air are unnecessary, andeven undesirable. The smoking taste and flavor is not appreciablyaltered when from about 0.3 to 1.0 volume of air per volume of smoke isemployed.

EXAMPLE XIV Sixty-five brand B cigarettes were treated by carefullyimmersing in a concentrated sodium perborate solution for ten seconds,draining, and drying to constant weight at 40 C. in a stream of airpassing at a rate of a cubic foot per minute containing moisture at 25mm. Hg vapor pressure. Care was exercised to avoid tearing the cigarettepapers. Dipping and drying were repeated until analysis of fivecigarettes showed a sodium perborate trihydrate content of 0.4 grams percigarette. These dried cigarettes were then smoked with a mechanicalsmoker, as in Example IV and XII. Analysis of the butt tobacco showedthat the nickel, iron and cobalt content had not changed from theinitial tobacco, and the scrubbing of the smoke showed no metal contentof the smoke. This example shows the equivalence of 30 ml. of oxygen(released from the additive) and air containing 30 ml. of oxygen foreliminating metal carbonyls from tobacco smoke.

EXAMPLE XV Brand A cigarettes made with porous paper accomplished anoverall dilution of smoke with 15% air (0.15 vol. air/vol. smoke) whichrepresents a decrease in dilution from 0.26 vol. air/vol. smoke for thefirst puflf, to 0.04 vol. air/vol. smoke for the last puff (at least 16%butt tobacco). From air dilution required for the substantially completeremoval of the metal carbonyls from the smoke of tobacco of brand A (0.4vol./ vol. of smoke) it is calculated that 0.08 volume of oxygen (20% of0.4 vol.) is required for complete removal of iron, nickel and cobaltcarbonyls from 0.1 volume of smoke, i.e., 40 ml. of oxygen for 500 ml.of smoke. Urea peroxide solution was prepared at about 10% concentrationin water (i.e., one mol of urea H adduct per 900 ml. water). Sixtyfivebrand A cigarettes were dipped carefully to immerse about 85% of thecolumn of tobacco by holding the filter tip in the fingers. The dippedcigarettes were dried as in Example XIV. The dipping and drying wererepeated until analysis of five of the dipped cigarettes showed thepresence of 0.28 gram of urea peroxide per cigarette. The smoke of sixtyof these treated cigarettes showed no content of metal carbonyls. Thiswas confirmed by analysis of the butt tobacco (16%) which showed nodifference in content of iron, nickel and cobalt from that of theoriginal tobacco. Thus the combination of air through the porous paperplus oxygen from the urea peroxide for the last puff equaled the effectobtained from equal oxyfien dilution when obtained with air alone(Examples IV and XII) and when obtained from an oxygen-releasingadditive alone (Example XIV). For a puff of 35 ml. volume, a total of2.8 ml. of oxygen is required for the purpose of my invention. In thepresent example, 0.28 ml. were supplied through the paper and 2.52 weresupplied by the urea peroxide (0.28+2.52=2.8). EXAMPLE XVI Ammoniumperborate solution (15%) was employed to impregnate pipe smoking tobaccobrand E containing micrograms iron/ gram of tobacco, 4 micrograms nickelper gram of tobacco, and 1.1 micrograms of cobalt per gram of tobacco.It was found more convenient to spray the tobacco with an aqueoussolution than to dip it, spraying at the rate of 14 ml. of solution pergram of tobacco at about 40 C. at reduced pressure (1 mm. Hg mercury Jso that 0.20 gram of the perborate were deposited per gram of tobacco. Apipe full (4 grams) was smoked by drawing air through the pipe andscrubbing system employing a water filter pump to draw the air throughthe pipe. The pipe was smoked to consume 3 grams of the tobacco. Theammonium perborate released 30 ml. D (STP) in the pipe smoke per gram oftobacco. The remaining tobacco was analyzed, and analysis confirmed thatno metal carbonyls were formed. The total smoke collected (following thescrubbers for removing the metal carbonyls) was measured at 1,500 ml.and showed no metal carbonyl formation. The dilution amounted to ml. ofoxygen per 1,500 ml. of smoke, or the equivalent of 0.3 volume of airper volume of smoke.

EXAMPLE XVII The outer leaves i.e. the wrapper of a cigar C, wereremoved and the remainder of the cigar was sprayed with tertiary butylhydroperoxide in acetone solution (50% It to obtain a uniformdistriubtion of the peroxide in the amount of 0.25 gram per gram ofcigar weight. After evacuation at 30 C. for an hour, the wrapper wasreplaced on the cigar and the latter was smoked-mechanically--by drawingtwo liters of air through the cigar until three quarters of the cigarwas smoked. The gas was collected after scrubbing the smoke with thealcoholic iodine solution and nitric acid. Again metal carbonylformation did not occur as found by analysis of the scrubbed solutionsand of the remaining 25% cigar. The dilution with oxygen amounted to0.06 volume per volume of smoke.

EXAMPLE XVlII Cigarette tobacco was removed from brand A cigarettes.One-half of this tobacco was sprayed with an 8% solution of lithiumperborate and was dried in vacuo at 40 C. The spraying and dryingoperation was repeated until the lithium perborate content was about 0.2grams per gram of tobacco and this was confirmed by analys1s of 5 gramsof treated tobacco. The other half of the tobacco was sprayed withdistilled water and dried at 40 C. to serve as control tobacco. In ado-it-yourself cigarettemaking machine the treated tobacco was used toroll 60 cigaretes using cigarette paper which had three holes of 2 cm.from one end. The diameter of the holes was l mm. The paper was 7 cm.long. Similarly, 60 controls were made with untreated tobacco. Insmoking the controls, 30% air dilution of the smoke was provided by theholes in the paper for the first puff. For the last puif with 16% of thetobacco in the butt, the dilution was only 5%; the resistance of thecolumn of tobacco was reduced to 16% of the original resistance so thatthere was corresponding decrease in the air drawn through the holes inthe paper. The average air dilution for the total smoke was 18%. Thedilution with oxygen was 3.6%. The results of analyses showed 200micrograms total carbonyls (3 micrograms nickel carbonyl) in the smoke.

When the lithium perborate treated cigarettes were smoked, the smoke wascompletely free of detectible amounts of iron, nickel, and cobaltcarbonyls. The oxygen dilution was calculated to be 12% for the firstputf (equivalent to 60% air dilution), 6% oxygen from air through theholes in the paper and 6% from the perborate additive; and 7% oxygendilution was calculated for the last puff; 1% from air through the holesand 6% from the additive.

EXAMPLE XIX Example XVIII was repeated using 0.25 gram of potassiumperoxydicarbonate (K C O instead of 0.2 gram lithium perborate per gramof tobacco. The results of the smoking test again showed no detectibleamounts of metal carbonyls; the smallest detectible amount from 60cigarettes being 0.1 microgram which is calculated to be less than 0.5part per billion, or less than half the threshold value set by thegovernment hygienists and also by the International Health Congress. Thecalculated oxygen dilution of the smoke was 8% (0.88 vol./vol. ofsmoke).

EXAMPLE XX Sixty grams of pipe tobacco brand E was treated with sodiumperoxy carbonate (NaCO solution according to the procedure of ExamplesXVIII and XVI to deposit 0.31 gram of the carbonate per gram of tobacco.The dried tobacco was smoked in 20 pipefuls and the smoke was found tobe free of metal carbonyls. The oxygen dilution of the smoke wascalculated to be 8%.

The controlled introduction of air into tobacco smoke may be attained invarious Ways in accordance with the instant invention. For filtercigarettes, the wrapping may contain perforations at a point about 10 tomm. ahead of the filter. For non-filter cigarettes, the perforations maybe made about 10 to 20 mm. ahead of the month end. Again, porous paperscan be used which permit l/l air dilution for the first puff, and whichdecrease to about 0.025/1 for the last puff at about 16% butt tobacco.Thus an overall average of about 50% and over dilution does noteliminate the carbonyls from tobacco smoke for the last pulls, and mustbe supplemented by oxygen-releasing additives for complete carbonylelimination. A more porous paper may be used if the degree of porosityis controlled throughout the smoking of the cigarette. This control ispossible to attain by coating the pores with a material that melts inthe range of 100 C., so that the pores open for a limited and controlledarea just behind the combustion zone. This would maintain a constantdilution by maintaining a constant open porous area in the cigarette.Cellulosic materials, such as alkyl cellulose, cellulose acetate,propionate, butyrate or mixed esters of cellulose, or waxes, such ascarnauba, polyethylene, and the like, may serve to seal the pores. Theselection of such materials would naturally be made on the basis of thepleasantness added to the smoke. Again, the filter length can belengthened and the butt tobacco eliminated. Replacement of the tobacco,which normally remains unsmoked, with more filter material for the airand the smoke will avoid metal carbonyl formation from traveling thesmoke further over tobacco at temperatures conductive to formation ofmetal carbonyls.

In pipe smoking, small air ducts can be built into the pipe, of thecorrect size to give the desired air dilution prior to inhalation by thesmoker. In cigars, small holes running through the cigar diametricallyan inch or more from the mouth end of the cigar can be utilized to givethe desired air dilution constant throughout the smoking of the cigar.

It is not intended herein to decide which provision is optimum for usein controlling the air dilution of tobacco smoke, since the inventionresides in eliminating the transition metal carbonyls, particularly ofiron, nickel and cobalt, from tobacco smoke, prior to inhalation by thesmoker, by controlled introduction of air into the tobacco smoke. It ispreferred to make such air introduction at about 2 cm. from the mouthend of the cigars, cigarettes,

or pipe.

Thus it has been demonstrated that harmful metal carbonyls can beeliminated from tobacco smoke by controlled air and/or oxygen dilutionfrom about 0.3 to 1 volume of air (or 0.06 to 0.20 vols. of oxygen) pervolume of smoke prior to inhalation by the smoker. Each manufacturer ofeach brand of cigarette must determine (1) what air dilution is requiredfor his supply of tobacco (also for pipe or cigars); and (2) whatporosity of paper plus amount of additive will give the requireddilution for a given draw resistance, the draw resistance depending onthe particle size and packing in the smoking device.

EXAMPLE XXI The safest pleasant smoke free of metal carbonyls wasobtained by eliminating the last one-third of the tobacco in theordinary size cigarette and the last one-half of the king size cigaretteand replacing it with cellulosic filter material to maintain the presentnormal draw resistance about 20 mm. of waterfor the whole cigarette. Theremoval of said tobacco eliminated a major portion of the source of themetal carbonyls by avoiding the further travel over tobacco of the smokecontaining carbon monoxide. This elimination of butt tobacco accompaniedby the use of a porous paper which permitted a 1/ 1 air dilution of thefirst putt and about 0.4/1 for the last puif. The cigarette paper was ofthe same length as for conventional cigarette B brand so that airintroduction occurs through the paper and cellulosic material whichreplaced the butt tobacco, as well as through the wall paper surroundingthe tobacco.

While there have been described herein what are at present considered tobe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that modifications and changes may be made withoutdeparting from the essence of the invention. Thus any desired means ofintroducing air into the tobacco smoke, following the combustion zone,and prior to entering the smoker, may be used, it being considereddesirable to pass the airdiluted smoke through a filter section offilter material other than tobacco to remove oxides, hydroxides, orother residue of the iron, nickel and cobalt carbonyl reaction productswith air. The type of filter material is non-critical and any otherwiseacceptable conventionally-used filter material such as cellulose esters,cellulose, alkyl cellulose, polystyrene, activated carbon, silica,silicates, alumina and the like, may be used. It is therefore to beunderstood that the exemplary embodiments are illustrative and notrestrictive of the invention.

What is claimed is:

1. A method of reducing metal carbonyls in cigarette tobacco smoke whichcomprises adding oxygen to the smoke in part derived from theincorporation of an oxygenating non-toxic peroxy compound in theburnable charge of the cigarette, said compound being selected from thegroup consisting of perborates, peroxides and percarbonates of alkaliforming metals and ammonium, tertiary butyl hydroperoxide and ureaperoxides, and in part from air introduced laterally through thecigarette wrapper, the peroxy compound evolving 0.06 to 0.2 volumes ofoxygen per volume of tobacco smoke, and the laterally introduced airconstituting 0.3-1 volumes per volume of smoke.

References Cited UNITED STATES PATENTS 2,429,567 10/1947 Sowa 1311402,992,647 7/ 1961 Figge 131--9 3,380,458 4/1968 Touey et a1 131--17FOREIGN PATENTS 75 8,429 10/ 1952 Great Britain. 876,669 9/ 1961 GreatBritain.

MELVIN D. REIN, Primary Examiner U.S. Cl. X.R. 131-15, 17,

